1. Field of Invention
The invention relates to a device for carrying out optical measurements in turbid media, including at least one coherent light source, a detector unit and a control unit.
The invention also relates to a method of measuring biological tissues by irradiating the tissue by light from at least one light source.
The invention also relates to a method of determining inhomogeneities in biological tissues by irradiating the tissue by light from a plurality of light sources.
2. Description of the Related Art
A device of the kind set forth is known from M. A. O'Leary et al., Physical Review Letters, Vol. 69, No 18, November 1992.
The known device is used to study the propagation of diffuse light in turbid media with the object of developing applications for the localization of objects in turbid media. A turbid medium is to be understood to mean a medium in which the transport of light energy density can be described essentially by the diffusion equation. It has been found that an amplitude-modulated laser source generates a travelling wave of the light energy density in a turbid medium. These waves are referred to as photon density waves. Photon density waves are scalar, damped travelling waves. Even though the waves are quickly attenuated, they have a defined wavelength, amplitude and phase at all points in the medium. A diffusion coefficient for light in the turbid medium and an absorption coefficient in the turbid medium can be determined from the amplitude and the phase. In a biomedical environment the described technique offers possibilities in respect of imaging of inhomogeneities in objects, for example small breast tumors.
It is a drawback of the known device that only one photon density wave is generated in the light source.